1. Field of the Invention
This invention relates to the field of devices for monitoring and analyzing networks. More particularly, this invention relates to devices for monitoring and analyzing the transmission quality of packet network telephony.
2. Description of the Problem
A current objective of telephony providers is to provide users with high-quality voice service through packet networks. Packet networks transmit communication in messages which are commonly known as packets. A packet is a message carrying data for communication between two network terminals, each having different IP addresses and port numbers. Packet networks carrying voice communications must be managed to ensure their performance quality.
Many voice communication and other real-time applications use the Real-time Transport Protocol (RTP) for the transmission of messages. RTP is described in Request for Comments (RFC): 1889 and 1890, which are each incorporated herein by reference. Real-time Control Protocol (RTCP), a subset of RTP and also described in RFC: 1889 and 1890, is a network packet that contains call quality metrics, providing information on the quality of a voice communication, or call, at that moment. The headers for these protocols include quality metrics containing current information on jitter, packet loss, and delay. RTCP provides feedback to an application about the quality of data distribution. Quality metrics are useful to the senders, the receivers and third-party monitors for the discovery of network problems. The sender can adjust its transmission based on the receiver report feedback. The receivers can determine whether a congestion is local, regional or global. Any type of network frame may carry quality metric.
These quality metrics are important to network administrators for the anticipation of performance changes and the diagnosis performance failures. Network administrators can use devices known as network analyzers to intercept messages containing quality metrics in order to assist in their monitoring and analysis of network performance. Network analyzers have historically tracked RTCP messages for VoIP signal traffic trends for the instantaneous reports of quality; however, network analyzers have not provided a way to provide the user information about the quality of a completed communication for the entire duration of the communication. Currently, RTCP only provides a means to determine quality of a communication at one moment in time. There is a need for a way to determine total call quality using the RTCP messages. The benefit of determining total call quality is that it gives the VoIP application the ability to provide enhanced and more accurate VoIP call quality calculations. This will allow network administrators to provide better voice and facsimile services to network users.
Furthermore, there is a need to provide call quality calculations in a way that operators in the data communications and telecommunications fields can both understand. Data communication operators are accustomed to jitter, packet loss, and delay information to help them determine network quality; therefore, the application of these statistics to call quality will make the information more useful and understandable to them. Telecommunications operators expect call quality to be determined by signal information. Call quality information should be provided to them in a way that is familiar to telecommunication operators.